This invention generally relates to plastic containers for retaining a commodity, and in particular a liquid commodity. More specifically, this invention relates to a plastic container having a square shoulder region tapered into a round foot print.
Numerous commodities previously supplied in glass containers are now being supplied in plastic, more specifically polyester and even more specifically polyethylene terephthalate (PET) containers. The manufacturers and fillers, as well as consumers, have recognized that PET containers are lightweight, inexpensive, recyclable and manufacturable in large quantities.
PET is a crystallizable polymer, meaning that it is available in an amorphous form or a semi-crystalline form. The ability of a PET container to maintain its material integrity is related to the percentage of the PET container in crystalline form, also known as the xe2x80x9ccrystallinityxe2x80x9d of the PET container. Crystallinity is characterized as a volume fraction by the equation:   Crystallinity  =            ρ      -              ρ        a                            ρ        c            -              ρ        a            
where xcfx81 is the density of the PET material; xcfx81a is the density of pure amorphous PET material (1.333 g/cc); and xcfx81c is the density of pure crystalline material (1.455 g/cc).
The crystallinity of a PET container can be increased by mechanical processing and by thermal processing. Mechanical processing involves orienting the amorphous material to achieve strain hardening. This processing commonly involves stretching a PET preform along a longitudinal axis and expanding the PET preform along a transverse or radial axis to form a PET container. The combination promotes what is known as biaxial orientation of the molecular structure in the container. Thermal processing involves heating the material (either amorphous or semi-crystalline) to promote crystal growth.
The marketing of beverages, particularly liquor, is strongly driven by the need to create and retain brand identification among consumers. One method of increasing brand recognition is the use of a particular container shape. As part of an overall marketing strategy, many beverage marketers have built brand identification based on container shapes having non-circular, particularly square cross sections. In many instances, the investment and benefit in identifying a product by its container configuration precludes changes in container configuration which would enhance manufacturing capabilities but potentially injure brand recognition.
Non-circular shaped containers create several problems during the manufacturing process. For example, square shaped containers must be kept in a particular orientation during filling, labeling and packaging which can significantly decrease production efficiency. Square shaped containers frequently can get caught on machine guides and stack up on the production line. Additionally, square shaped containers require inspection of all four sides in order to locate an appropriate flat surface for labeling. Accordingly, required rotation mechanisms are more complicated. Thus, square shaped containers frequently require re-orientation on the production line, decreasing labeling accuracy, production speed and efficiency.
The outer panels or sides of a square shaped plastic container often sink in and deform due to xe2x80x9cshrink backxe2x80x9d. This phenomenon is magnified under vacuum conditions created by warm fill (i.e., liquid product filled into the container while the liquid product is at an elevated temperature, typically above ambient temperature but below about 54xc2x0 C. (130xc2x0 F.)) and cool down. Such sink in and deformation is caused, in part, by a decrease in rigidity found in the outer panels or sides of square shaped plastic containers relative to traditional glass containers. The above described sunken panels cause labeling issues such as rippled labels, poor label adhesion and decreased reliability of automatic processes. One solution to the above described sunken panels has been an attempt to increase panel rigidity by increasing the thickness of the panel through the addition of material. Such an increase in material, however, significantly increases container cost.
Traditional circular shaped plastic containers do not exhibit the sunken panel phenomenon. The curvature of the sidewalls found in a circular shaped plastic container tend to resist buckling better than a flat panel surface. Thus, there is a need for an improved plastic container which maintains brand identity by creating the visual perception of a square shaped container while incorporating the material handling, labeling and structural benefits of a circular shaped container. Compound panel curvature greatly reduces potential panel shrink back.
It is, therefore, a principal object and purpose of the present invention to provide a plastic container that provides the handling, labeling and structural benefits of a circular shaped container while preserving the brand identification benefits of a square shaped container.
It is an additional principal object and purpose of the present invention to provide a plastic container that does not require frequent re-orientation on the production line, thus increasing labeling accuracy, production speed and efficiency.
It is another object and purpose of the present invention to provide a plastic container that provides increased rigidity and resists panel shrink back.
It is still another object and purpose of the present invention to provide a plastic container having lower resin costs and increased production line efficiencies.
It is another object and purpose of the present invention to provide a plastic container that has a square shoulder region which gradually tapers into a round foot print.
These and other objectives and advantages are provided by the present invention which is directed to a plastic container that provides the handling, labeling and structural benefits of a circular shaped container while preserving the brand identification benefits of a square shaped container. The plastic container includes a neck having a mouth defining an opening into the container, a shoulder region extending from the neck to a body portion, the body portion extending from the shoulder region to a base, the base closing off an end of the container. The neck, shoulder region, body portion and base cooperating to define a receptacle chamber within the container into which product can be filled. The shoulder region has a substantially square cross section while the base has a substantially circular cross section. Consequently, the plastic container creates the visual perception of a square shaped container while incorporating the material handling, labeling and structural benefits of a circular shaped container.
A second embodiment of the invention includes a neck having a mouth defining an opening into the container, a shoulder region having a substantially square cross section, a body portion and a base having a substantially circular cross section. The body portion including pinch grips.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.